Piston for internal-combustion engines



E. A. SPERRY PISTON FOR INTERNAL COMBUSTION ENGINES Filed July 20. 1921 Aug. 16 1927.

Patented Aug. 16, 1927.

1,639,062 PATENTV OFFICE.

ELMER A. sPERRY, E BRooKLirN, "NEW YORK, AssIGNoR fro sPERRY DEVELOPMENT COMPANY, 0E DovER GREEN, DELAWARE, A CORPORATION 0E DELAWARE.

IPISTON FORFINTRNAL-COMBUSTION ENGINES.

Application filed iliily` 20, `1921. Serial No. 486,181.

This invention relates to'pistons for internal combustion engines especially to engines employing very high pressures and temperatures, such as multiple expansion and Diesel engines.

As is now well understood, the solution of the problem of cooling the piston of such an engine lies in abstracting vheat from the head of the piston as rapidly as possible-.-

lo For this purpose it has been proposed to' water cool the under surface of the piston head by circulating water through the top of the piston from an external source. This method, however, involves the use of sliding l5 parts and introduces serious complications. I prefer, therefore, to transfer the heat from the head of the piston to the cooled cylinder walls byutilizing a Huid sealed. within the piston head which rapidly con- 2" veys the heat from the piston head to the thin walls thereof which lie in close contact with the water cooled cylinder walls.

Referring to Vthe drawings in which what I now consider the preferred form of my invention is shown:

Fig. 1 is a vertical section of one form of my improved piston.

Fig. 2 is a similar view of an alternative form; the section also being taken at right angles to the section shown in Fig. -1. ,l

Fig. 3 is a view similar to Fig. 1 of a third alternative form. y

Fig. 4 is a detail showing two positions. A and B, of the operating mechanism of 5 Fig. 1 for causing circulation of the liquid.

Fig. 5 is a detail taken at right angles to F ig. 4.

Fig. 6 is a detail showing one method of filling the piston shown in Fig. 3.

According to one form of the invention, I completely till the interior 1 of the piston 2 with a non-volatile liquid of fairly good heat conductivity and low viscosity. For this purpose I have found certain -grades of oil having the above characteristics as an excellent liquid.

A. filling plug (or plugs) 3 1s shown as threaded in aperture 3 in the piston through which the liquid is forced-into the piston. Said aperture 3 preferably registers with valve or equivalent openings 50 in the cylinder cavity below', so that ready access may be had through such opening to the filling aperture. Preferably, the under surface of the piston head is provided with heat radiat- 55 ing tins 5vor baliie plates which project into the oil. Also within said base is a separating diaphragm 6 shown as dome-shaped. The purpose of said diaphragm is to assist the, natural circulation of the oil upwardly along the hotter portion of the piston and downwardly in the cooler parts thereof, as indicated by the arrows 7. Said domeshaped diaphragm is open at the bottom and also has a hole 8 at the top thereof in which G5 may be placed a propeller 9 also for assisting the circulation of the oil. Said propeller is shown as mounted on Ja shaft 10 journaled at the top in the boss 11 of the piston head and at the bottom'in the block 70 12 supporting the crank pin 32.

For rotating said propeller I prefer to employ inertia. means operated by the continuous stopping and starting of the piston as it reciprocates. Said means is shown as a small weight. 13 mounted on stub shafts 14 and 15 slidably and rotatably journalled in inclined bearings 16 and 17 on top of the block 12. Secured to said weight are a pair of downwardly extending arms 18. and 19 which are adapted to engage alternately ratchet wheel 20 on the shaft 10 of said propeller. The propeller is rotated in the same direction when the weight is moved upwardly as when it is moved downwardly since when the weight is flopped upwardly by a sudden stopping of the piston on its upward stroke, or by the sudden starting of the piston on the downward stroke, the weight will also slide upwardly .in the in clined bearings 16 and 17 or to the right in Fig. 1. so that the pawl 18 will be brought into engagement with the ratchet wheel 20 at that time. asshown in Fig. 1 and view A of Fig. 4; This. it will be seen, will rotate the ratchet wheel clockwise in Fig. 4, view A. On the other hand, when the pist-on suddenly stops at the end of its downwarl stroke, or starts on its upward stroke, the weight will flop downwardl y and also slide to the left in F ig: 1, there vy bringing the pawl 19 into engagement Withthe ratchet wheel (see view B, Fig. 4). This, it will be seen, will also rotate the ratchet Wheel clockwise in Fig. 4.

For allowing for the expansion and contraction of the oil filling said space in the piston, I have shown flexible wall airtight members '25, 26 which expand and contract to allow for the contraction and expansion of the oil.

By inspection of the arrows in Fig. 1, .it will be seen that the cooler oil may be drawn 'up through the center of the space by the propeller and.l forced against the under surface of the hot piston head from whence it iiows downwardly against the'walls of the piston and imparts the heat acquired from Ythe piston head to said thinwalls from where it is transferredy by conduction to the water cooled cylinder walls 27, as shown by full line arrows 7 or, if desired, the oil may be caused to flow in the opposite direction as shown by dotted linevarrows 7 by varying the pitch of the blades.

I do not limit myself, however, to the employment of a liquid within the piston, but may employ any fluid, including air or other gas, in connection with the form shown vin- Fig. 1, i. e., when a positive means suchv as. fan 9 is employed to cause continuous circulation of the fluid within the piston.

In the form shown in Figs. 2* and 3 I prefer to only partially iill space l within they piston by oil-or similar liquid. In this form of the invention since the space is only partially filled, no artificial means for circulating the oil need be employed as the reciprocation of the piston will servev to splash the oil over all surfaces, rapidly throwing the oil from the hotter upper surface 'of the piston against the cooler walls thereof. I

find it preferable, however, to provide within said space a bailie member 28 for assisting in distributing the oil and for imparting a swirling motion thereto. For this purpose I have shown the interior of said member 28 as provided with spiral ribs 29. The oil will then emerge from the restricted opening 30 therein in a swirling condition, so that it will spread out against the entire end surface of the top of the piston and over the downwardly projecting ribs connected thereon.

It should also be noted that' I prefer to construct the iston itself with a large downwardly exten ing trunk 30 which is guided in the guide 31 secured or formed as a part of the lower portion of the cylinder.

It should he noted then that the piston is supported and guided by two spaced surfaces. In addition, I prefer to extend the piston below the point where the wrist pgi'n 32 is mounted therein, as shown at 33.l y this means a' three point guide is secured for the piston, two of which, at least, are near and on -opposite sides of the wrist pin connection, so that there is no tendency to twist the piston out of alignment with the cylinder. The 'connecting-rod 34 extends downwardly from said pin to the usual crank shaft (not shown).

It should be noted that the type lof engine illustrated is one wherein the connecting rod 34 is pivoted within the cylinder itself on ywrist pin 32, the iston possessingvno pistonv rod or cross headl the connecting rod exerts lateral pressure on the piston, first to the right and then to the yleft (Fig. 1), or in other words, at right Aangles to the axis ofthe wrist pin, as the rod reciprocates with `the piston and oscillates with the revolving crank. This lateral pressure serves to bring the piston wallsinto intimate contact with the cylinder walls along the surfaces affected,` thereby greatly In this type of engine, y

assisting the transfer of heat from the piston to the water jacketed cylinder. As is well known, an'appreciable clearance is allowed lbetween the piston and cylinder walls, which is usually lled with a film or films of oil, the

thickness of which depends upon the clearanceand upon the`direction of pressure of tue cylinder. With an engine .ofthe .type

described, the thickness of the oil film is I reduced to a minimum when pressure is exerted against 'that side of the piston, thereby decreasing thermal resistance of the parts. lt is for this reasonalso that I prefer to circulate the oil or other fluid along these surfaces which lie normal to the crank pin, (see Figs. l and 2), since it is these surfaces which are brought into most intimate contact with the cylinder walls. -While the threepoint guidehereinbefore described prevents twisting of thelongitudinal axis of the piston-head relative to the longitudinal axis of ythe cylinder, it does not prevent lateral movement of said firstv axis parallel to ysaid second axis due to thinning out of the oil'.

. iilm between thepiston and cylinder dueV to the thrust of the connecting rod. This displacement is, however, extremely small, but

through said pipe 38 and into the piston.

On the other hand, when it is desired to re-I y move the oil from the piston, a flexible pipe 40 is inserted through the pipe 38 until there'is suiiicient of the pipe to extend down to the bottom of the piston, as villustrated in dotted lines. The oil is then siphoned Vout of the piston. Said pipe may extend just above the normal level of the liquid and, hence, may be used as an overflow pipe to predetermine the level of the liquid. It will be understood that in this form of the invention also, aper- 115 6 and the desired amount ofoil then is forced may be provided in the base of the cylinder to give access to the filling and overflow tube.

I find the 'following characteristlcs essential for the oil or other liquid employed:

Where the oil entirely fills the space, it is essential that it be absolutely free from either water or air. If any water 1s present,

the high temperature conditions will generate steam very materially and perhaps dangerously increase the pressure within the cavity. If air is present, on the other hand. the oxygen of the air mayoxidlze a portion of the oil', leaving a carbon deposlt on the cylinder wall. The oil employed should also have a low viscosity even when cooled so that it will circulate freely from the first and not wait until the parts get too hot before circulation starts in. Another requisite is thatthe oil must have as high heat conductivity as lcan be obtained. Next, the oil should have a high specific heat and an extremely high boiling point, so as not to generate pressure or cause overheating. The oil should also possess high vapor tension so as not to vaporize easily under its boiling point. Where the pistonv is only partially full and no diaphragmis employed or where partially full and a diaphragm 1s employed, the part not iilled with oil should be filled with an inert or non-oxidizing gas,

preferably a reducing gas, such as hydrogen. The trouble with air is that it oxidizes part of the hydrogen in the hydrocarbon, leaving the carbon free to deposit. The carbon deposits act.as a charcoal filling in arefrig- 'erated wall, i. e. as a non-conductor of vheat and reduces the eficiency of cooling. The oil must also be such as will not yield metallic salts or emulsify in contact with the metal walls of the piston.

In accordance with the provisions'of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus, which I now consider to represent the best `embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the. invention can be carried out by other means. Also, while it is designed to use the variousfeaftures and elements in l\the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. The combination with an internal combustion engine, of a hollow piston therefor having sealed therein oil or liquid having similar physical characteristics and means he piston comprising a rotary propeller 2. The combination with an internal combustion' engine, of a hollow piston therefor having sealed therein oil or liquid having similar physical characteristics and means for assisting the circulation of the oil within the piston comprising a rotary propeller fan and inertia operated means for rotating said propeller fan.

3. The combination with an internal combustionengine, of'a hollow piston therefor forming a sealed chamber, said piston being completely filled with a heat-conducting fluid.

4. The combination-with an internal combustion engine, of 1a hollow piston therefor having sealed therein a liquid of high vapor tension and low-viscosity and compressible -means permitting expansion and contraction of said liquidwithin said piston.

5. The combination with an internal combustion engine, of a hollow piston therefor forming a sealed chamber, said piston being completely filled with oil.

6. The combination with an internal coinl i similar physical characteristics and means for assisting the circulation of the oil within the piston comprising guides and a rotary propeller fan for. assisting convection currents.

7. The combination with an internal combustion engine, of a hollow piston therefor adapted to contain and have sealed therein a liquid and a., normally closed filling pipe extending within said hollow piston.

8. The combination with an internal combustion engine, of a hollow piston therefor, said piston being completely filled with oil, and means within said piston. for circulating the oil through a predetermined circuit.

9. The combination with an internal combustion engine having a cylinder, of a hollow piston therefor. adapted to contain a liquid and having a filling aperture, and an opening in said cylinder registering with said aperture to provide accessto the same.

l0. The .combination with an internal combustion engine, of a hollow piston therefor. sald piston being completely filled with `oil, and a rotary fan within said piston for prising a propeller, a movable weight opy erated by reciprocation of the piston and means connecting said weight and said propeller continuously to advance the propeller ur one direction as the piston reciprocates.

In testimony whereof I have afiiXed my signature. Y

c ELMER A. SPERRY. 

